Mon. Not. R. Astron. Soc., 403, 996-1008 (2010/April-1)
Hierarchical structures in the Large and Small Magellanic clouds.
BONATTO C. and BICA E.
Abstract (from CDS):
We investigate the degree of spatial correlation among extended structures in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). To this purpose, we work with subsamples characterized by different properties such as age and size, taken from the updated catalogue of Bica et al. or gathered in the present work. The structures are classified as star clusters or non-clusters (basically, nebular complexes and their stellar associations). The radius distribution functions follow power laws (dN/dR ∝ R–α) with slopes and maximum radius (Rmax) that depend on object class (and age). Non-clusters are characterized by α ~ 1.9 and Rmax≲ 472pc, while young clusters (age ≲10Myr) have α ~ 3.6 and Rmax≲ 15pc and old ones (age ≳600Myr) have α ~ 2.5 and Rmax≲ 40pc. Young clusters present a high degree of spatial self-correlation and, especially, correlate with star-forming structures, which does not occur with the old ones. This is consistent with the old clusters having been heavily mixed up, since their ages correspond to several LMC and SMC crossing times. On the other hand, with ages corresponding to fractions of the respective crossing times, the young clusters still trace most of their birthplace structural pattern. Also, small clusters (R < 10pc), as well as small non-clusters (R < 100pc), are spatially self-correlated, while their large counterparts of both classes are not. The above results are consistent with a hierarchical star formation scenario for the LMC and SMC.
© 2010 The Authors. Journal compilation © 2010 RAS
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